A FINGERPRINT is all you need to determine whether someone is under the influence of drugs.

Paul Yates from Intelligent Fingerprinting, a company spun out from the University of East Anglia in Norwich, and colleagues, have developed a handheld device that police can use to detect breakdown products from drugs excreted through sweat pores in the fingertips.

The device applies gold nanoparticles coated with antibodies to a fingerprint. The antibodies stick to antigens on specific metabolites in the fingerprint. Fluorescent dyes attached to the antibodies will highlight the presence of any metabolites. The technique was first used to detect nicotine, but now works on a range of drugs, including cocaine, methadone and cannabis.

It is hard to prove that someone is drug driving, for example, says Yates, because existing tests are invasive, can be contaminated, or aren't sensitive enough. The new device could detect nanograms of metabolites in minutes, he says. The device was announced at the UCL International Crime Science Conference in London last week.